Taxol is a naturally occurring compound which has shown great promise as an anti-cancer drug. For example, taxol has been found to be an active agent against drug-refractory ovarian cancer by McGuire et al. See "Taxol: A Unique Anti-Neoplastic Agent With Significant Activity Against Advanced Ovarian Epithelial Neoplasms," Ann. Int. Med., 111, 273-279 (1989). All patents, scientific articles, and other documents mentioned herein are incorporated by reference as if reproduced in full below.
Unfortunately, taxol has extremely low solubility in water, which makes it difficult to provide a suitable dosage form. In fact, in Phase I clinical trials, severe allergic reactions were caused by the emulsifiers administered in conjunction with taxol to compensate for taxol's low water solubility; at least one patient's death was caused by an allergic reaction induced by the emulsifiers. Dose limiting toxicities include neutropenia, peripheral neuropathy, and hypersensitivity reactions.
Brown et al, in "A Phase I Trial of Taxol Given By A 6-Hour Intravenous Infusion" J of Clin Oncol, Vol. 9, No. 7, pp. 1261-1267 (July, 1991) report on a Phase I Trial in which taxol was provided as a 6-hour IV infusion every 21 days without premedication. 31 patients received 64 assessable courses of taxol. One patient had a severe (or acute) hypersensitivity reaction, which required discontinuation of the infusion and immediate treatment to save the patients life. Another patient experieinced a hypersensitivity reaction, but it was not so sever as to require discontinuing the infusion. Myelosuppression was dose-limiting, with 2 fatalities due to sepsis. Non-hematologic toxicity was of Grade 1 and 2, except for one patient with Grade 3 mucositis and 2 patients with Grade 3 neuropathy. The neuropathy consisted of reversible painful paresthesias, requiring discontinuation of taxol in two patients. Four partial responses were seen (3 in patients with non-small-cell lung cancer, and one in a patient with adenocarcinoma of unknown primary). The maximum tolerated dose reported was 275 mg/m.sup.2, and the recommended Phase II starting dose was 225 mg/.sup.2. The incidence of hypersensitivity reaction was reported to be schedule-dependent, with 6 to 24-hour infusions of drug having a 0% to 8% incidence of hypersensitivity reactions. It was also reported that hypersensitivity reactions persist with or without premedication despite prolongation of infusion times. Since these Phase I studies were conducted on terminally ill patients suffering from a variety of cancers, the efficacy of the taxol treatments could not be determined.
In a study by Kris et al., taxol formulated with Cremaphor EL in dehydrated alcohol was given as a 3-hour IV infusion every 21 days, with the administered dosage ranging from 15 to 230 mg/m.sup.2 in nine escalation steps. Kris et al. concluded that "with the severity and unpredictability of the hypersensitivity reactions, further usage of taxol is not indicated with this drug formulation on this adminstration schedule." See Cancer Treat. Rep., Vol. 70, No. 5, May 1986.
Since early trials using a bolus injection or short (1-3 hour) infusions induced anaphylactic reactions or other hypersensitivity responses, further studies were carried out in which taxol was administered only after premedication with steroids (such as dexamethasone), antihistamines (such as diphenhydramine), and H.sub.2 -antagonists (such as cimetidine or ranitidine), and the infusion time was extended to 24 hours in an attempt to eliminate the most serious allergic reactions. Various Phase I and Phase II study results have been published utilizing 24-hour infusions of taxol with maximum total dosages of 250 mg/m.sup.2, generally with the course being repeated every 3 weeks. Patients were pretreated with dexamethasone, diphenhydramine, and cimetidine to offset allergic reactions. See Einzig, et al., "Phase II Trial of Taxol in Patients with Metastatic Renal Cell Carcinoma," Cancer Investigation, 9(2) 133-136 (1991), and A. B. Miller et al., "Reporting Results of Cancer Treatment," Cancer, Vol 47, 207-214 (1981).
Koeller et al, in "A Phase I Pharmacokinetic Study of Taxol Given By a Prolonged Infusion Without Premedication," Proceedings of ASCO, Vol. 8 (March, 1989), recommends routine premedication in order to avoid the significant number of allergic reactions believed to be caused by the cremaphor (polyethoxylated castor oil) vehicle used for taxol infusions. Patients received dosages ranging from 175 mg/m.sup.2 to 275 mg/m.sup.2.
Wiernik et al, in "Phase I Clinical and Pharmacokinetic Study of Taxol," Cancer Research, 47, 2486-2493 (May 1, 1987), also report the administration of taxol in a cremaphor vehicle by IV infusion over a 6-hour period in a Phase I study. Grade 3-4 hypersensitivity reactions incurred in 4 of 13 courses. The starting dose for the study was 15 mg/m.sup.2 (one-third of the lowest toxic dose in dogs). Doses were escalated, and a minimum of 3 patients were treated at each dose level until toxicity was identified, and then 4-6 patients were treated at each subsequent level. The study concluded that neurotoxicity and leucopenia were dose-limiting, and the recommended Phase II trial dose was 250 mg/m.sup.2 with premedication.
Other exemplary studies on taxol include: Legha et al, "Phase II Trial of Taxol in Metastatic Melanoma," Vol. 65 (June 1990) pp. 2478-2481; Rowinsky et al, "Phase I and Pharmacodynamic Study of Taxol in Refractory Acute Leukemias," Cancer Research, 49, 4640-4647 (Aug. 15, 1989); Grem et al, "Phase I Study of Taxol Administered as a Short IV Infusion Daily For 5 Days," Cancer Treatment Reports, Vol. 71 No. 12, (December, 1987); Donehower et al., "Phase I Trial of Taxol in Patients With Advanced Cancer," Cancer Treatment Reports, Vol. 71, No. 12, (December, 1987); Holmes et al, "Phase II Study of Taxol in Patients (PT) with Metastatic Breast Cancer (MBC)," Proceedings of the American Society of Clinical Oncology, Vol. 10, (March, 1991), pp. 60. See also Suffess, "Development of Antitumor Natural Products at the National Cancer Institute," Gann Monograph or Cancer Research, 31 (1989) pp. 21-44 (which recommends that taxol only be given as a 24-hour infusion).
Weiss et al., in "Hypersensitivity Reactions from Taxol," Journal of Clinical Oncology, Vol. 8, No. 7 (July 1990) pp. 1263-1268, reported that it was difficult to determine a reliable overall incidence of hypersensitivity reactions, HSRs, because of the wide variations in taxol doses and schedules used, and the unknown degree of influence that changing the infusion schedule and using premedication has on HSR incidents. For example, of five patients who recieved taxol in a 3-hour infusion at greater than 190 mg/m.sup.2 with no premedication, three had reactions, while only one out of 30 patients administered even higher doses over a 6-hour infusion with no premedication had a reaction. Therefore, this suggests that prolonging the infusion to beyond 6 hours is sufficient to reduce HSR incidents. Nevertheless, Weiss et al. found that patients receiving 250 mg/m.sup.2 of taxol administered via a 24-hour infusion still had definite HSRs. Thus, while prolonging drug infusion to 6 or 24-hours may reduce the risk for an acute reaction, this conclusion can not be confirmed, since 78% of the HSR reactions occurred within ten minutes of initiating the taxol infusion, which indicates that the length of time planned for the total infusion would have no bearing. Further, concentration of taxol in the infusion may also not make a difference since substantial numbers of patients had reactions to various small taxol dosages. Finally, not only is the mechanism of taxol HSR unknown, it is also not clear whether taxol itself is inducing HSRs, or if the HSRs are due to the excipient (Cremophor EL; Badische Anilin und Soda Fabrik AG [BASF], Ludwigshafen, Federal Republic of Germany). Despite the uncertainty as to whether or not premedication hadany influence on reducing the severity or number of HSRs, prophalactic therapy was recommended, since there is no known danger from its use.
The conflicting recommendations in the prior art concerning whether premedication should be used to avoid hypersensitivity reactions when using prolonged infusion durations, and the lack of efficacy data for infusions done over a six hour period has led to the use of a 24-hour infusion of high doses (above 170 mg/m.sup.2) of taxol in a Cremaphor EL emulsion as an accepted cancer treatment protocol.
Although it appears possible to minimize the side effects of administering taxol in an emulsion by use of a long infusion duration, the long infusion duration is inconvenient for patients, and is expensive due to the need to monitor the patients for the entire 6 to 24-hour infusion duration; Further, the long infusion duration requires that patients spend at least one night in a hospital or treatment clinic.
Thus, it is highly desirable to develop a taxol infusion protocol which would allow for recipients to be treated on an out-patient basis. Since taxol infusions are generally preceded by premedication, and require post-infusion monitoring and record keeping, it is highly desirable that the infusion duration not exceed 6 hours, yet the infusion dosage should provide the patient sufficient taxol to have an anti-neoplastic effect, while not exceeding dose-limiting toxicities. It is also desirable to minimize premedication since this increases patient discomfort and increases the expense and duration of treatment.
Even if infusion duration can not be shortened, it is also desirable to avoid the high dosages of taxol presently believed necessary to have an anti-neoplastic effect, which induce a variety of adverse side-effects, including respiratory distress, cardiovascular irregularities, flu-like symptoms, gastrointestinal distress, hematologic complications, genitourinary effects, neuropathy, alopecia, and skin rashes.
Further, due to the extremely limited supply of taxol, and the high dosage requirement for each patient, the demand for taxol greatly exceeds the supply.
Therefore, it is highly desirable to reduce taxol dosages, if possible, to both extend the supply of taxol and reduce the toxic side effects of taxol. It is also highly desirable to decrease the time required to administer taxol to patients to minimize patient discomfort and expense.
Thus, there is a need for a new method of administration of taxol which utilizes less taxol and/or requires less infusion time.
Therefore, it is a primary object of the present invention to provide a new method for administering taxol over a shorter period of time than the present 6 to 24-hour infusion protocols, while minimizing toxic effects induced by the administration of taxol.
It is another object of the present invention to provide a new method for administration of taxol which reduces the amount of taxol administered to a patient, without sacrificing the anti-neoplastic effects desired by administering taxol.
It is yet a further object of the present invention to provide a new method for administration of taxol which utilizes both lower dosages of taxol and shorter infusion periods, without sacrificing the anti-neoplastic benefits of the administration of taxol.